Introduction to Computers
Computer
A computer is an electronic device, operating under the control of instructions stored
in its own memory that can accept data (input), process the data according to specified
rules, produce information (output), and store the information for future use
1
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Functionalities of a computer2
Any digital computer carries out five functions in gross terms:
Any kind of computers consists of HARDWARE AND SOFTWARE.
Hardware:
Computer hardware is the collection of physical elements that constitutes a computer
system. Computer hardware refers to the physical parts or components of a computer
such as the monitor, mouse, keyboard, computer data storage, hard drive disk (HDD),
system unit (graphic cards, sound cards, memory, motherboard and chips), etc. all of
which are physical objects that can be touched. 3
1
Vermaat, Misty E. Microsoft Office 2013 Introductory. Cengage Learning, p.IT3. 2014
2
3
Input Devices
Input device is any peripheral (piece of computer hardware equipment to provide data
and control signals to an information processing system such as a computer or other
information appliance.
Input device Translate data from form that humans understand to one that the computer
can work with. Most common are keyboard and mouse
Example of Input Devices:-
1. Keyboard
2. Mouse (pointing device)
3. Microphone
4. Touch screen
5. Scanner
6. Webcam
7. Touchpads
8. MIDI keyboard
9.
10.Graphics Tablets
11.Cameras
12.Pen Input
13.Video Capture Hardware
14.Microphone
15.Trackballs
16.Barcode reader
17.Digital camera
18.Joystick
19.Gamepad
20.Electronic Whiteboard
21.
Note: The most common use keyboard is the QWERTY keyboard. Generally standard Keyboard
has 104 keys.3
Central Processing Unit (CPU)
A CPU is brain of a computer. It is responsible for all functions and processes.
Regarding computing power, the CPU is the most important element of a computer
system.
The CPU is comprised of three main parts :
* Arithmetic Logic Unit (ALU): Executes all arithmetic and logical operations.
Arithmetic calculations like as addition, subtraction, multiplication and division.
Logical operation like compare numbers, letters, or special characters
* Control Unit (CU): controls and co-ordinates computer components.
1. Read the code for the next instruction to be executed.
2. Increment the program counter so it points to the next instruction.
3. Read whatever data the instruction requires from cells in memory.
4. Provide the necessary data to an ALU or register.
5. If the instruction requires an ALU or specialized hardware to complete, instruct
the hardware to perform the requested operation.
* Registers :Stores the data that is to be executed next, "very fast storage area".
Primary Memory:-
1. RAM: Random Access Memory (RAM) is a memory scheme within the computer
system responsible for storing data on a temporary basis, so that it can be promptly
accessed by the processor as and when needed. It is volatile in nature, which means
that data will be erased once supply to the storage device is turned off. RAM stores
data randomly and the processor accesses these data randomly from the RAM
storage. RAM is considered "random access" because you can access any memory
cell directly if you know the row and column that intersect at that cell.
2. ROM (Read Only Memory): ROM is a permanent form of storage. ROM stays
active regardless of whether power supply to it is turned on or off. ROM devices
do not allow data stored on them to be modified.
Secondary Memory:-
Stores data and programs permanently :its retained after the power is turned off
1. Hard drive (HD): A hard disk is part of a unit, often called a "disk drive," "hard drive," or "hard
disk drive," that store and provides relatively quick access to large amounts of data on an
electromagnetically charged surface or set of surfaces.
2. Optical Disk: an optical disc drive (ODD) is a disk drive that uses laser light as part of the process
of reading or writing data to or from optical discs. Some drives can only read from discs, but recent
drives are commonly both readers and recorders, also called burners or writers. Compact discs,
DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by
such drives. Optical drive is the generic name; drives are usually described as "CD" "DVD", or
"Bluray", followed by "drive", "writer", etc. There are three main types of optical media: CD,
DVD, and Blu-ray disc. CDs can store up to 700 megabytes (MB) of data and DVDs can store up
to 8.4 GB of data. Blu-ray discs, which are the newest type of optical media, can store up to 50
GB of data. This storage capacity is a clear advantage over the floppy disk storage media (a
magnetic media), which only has a capacity of 1.44 MB.4
3. Flash Disk
A storage module made of flash memory chips. A Flash disks have no mechanical platters or access
arms, but the term "disk" is used because the data are accessed as if they were on a hard drive. The
disk storage structure is emulated.
Output devices
An output device is any piece of computer hardware equipment used to communicate
the results of data processing carried out by an information processing system (such
as a computer) which converts the electronically generated information into human
readable form.
Example on Output Devices:
1. Monitor
2. LCD Projection Panels
3. Printers (all types)
4. Computer Output Microfilm (COM)
5. Plotters
6. Speaker(s)
7. Projector
Note Basic types of monitors are a.Cathode Ray Tube (CRT). B. Liquid Crystal Displays (LCD).
c.light-emitting diode (LED).
Printer types: 1-Laser Printer. 2-Ink Jet Printer. 3-Dot Matrix Printer
1. Computer Software
Software
Software is a generic term for organized collections of computer data and instructions,
often broken into two major categories: system software that provides the basic non
task-specific functions of the computer, and application software which is used by
users to accomplish specific tasks.
Software Types
A. System software is responsible for controlling, integrating, and managing the
individual hardware components of a computer system so that other software and
the users of the system see it as a functional unit without having to be concerned
with the low-level details such as transferring data from memory to disk, or
rendering text onto a display. Generally, system software consists of an operating
system and some fundamental utilities such as disk formatters, file managers,
display managers, text editors, user authentication (login) and management tools,
and networking and device control software.
B. Application software is used to accomplish specific tasks other than just running
the computer system. Application software may consist of a single program, such
as an image viewer; a small collection of programs (often called a software
package) that work closely together to accomplish a task, such as a spreadsheet or
text processing system; a larger collection (often called a software suite) of related
but independent programs and packages that have a common user interface or
shared data format, such as Microsoft Office, which consists of closely integrated
word processor, spreadsheet, database, etc.; or a software system, such as a
database management system, which is a collection of fundamental programs that
may provide some service to a variety of other independent applications.
Comparison Application Software and System Software
System Software
Application Software
Computer software, or just software is a
general term primarily used for digitally stored
data such as computer programs and other
kinds of information read and written by
computers. App comes under computer
software though it has a wide scope now.
Application software, also known as an
application or an "app", is computer software
designed to help the user to perform specific
tasks.
Example:
1) Microsoft Windows
2) Linux
3) Unix
4) Mac OSX
5) DOS
1) Opera (Web Browser)
2) Microsoft Word (Word Processing)
3) Microsoft Excel (Spreadsheet software)
4) MySQL (Database Software)
5) Microsoft PowerPoint (Presentation Software)
6) Adobe Photoshop (Graphics Software)
Interaction:
Generally, users do not interact with system
software as it works in the background.
Users always interact with application software
while doing different activities.
Dependency:
System software can run independently of the
application software.
Application software cannot run without the
presence of the system software.6
Unit of Measurements
Storage measurements: The basic unit used in computer data storage is called a bit
(binary digit). Computers use these little bits, which are composed of ones
and zeros, to do things and talk to other computers. All your files, for
instance, are kept in the computer as binary files and translated into words
and pictures by the software (which is also ones and zeros). This two
number system, is called a “binary number system” since it has only two
numbers in it. The decimal number system in contrast has ten unique digits,
zero through nine.
Computer Storage units
Bit
BIT
0 or 1
Kilobyte
KB
1024 bytes
Megabyte
MB
1024 kilobytes
Gigabyte
GB
1024 megabytes
Terabyte
TB
1024 gigabytes
Size example
• 1 bit - answer to an yes/no question
• 1 byte - a number from 0 to 255.
• 90 bytes: enough to store a typical line of text from a book.
• 4 KB: about one page of text.
• 120 KB: the text of a typical pocket book.
• 3 MB - a three minute song (128k bitrate)
• 650-900 MB - an CD-ROM
• 1 GB -114 minutes of uncompressed CD-quality audio at 1.4 Mbit/s
• 8-16 GB - size of a normal flash drive
Speed measurement: The speed of Central Processing Unit (CPU) is measured by
Hertz (Hz), Which represent a CPU cycle. The speed of CPU is known as Computer
Speed.
CPU SPEED MEASURES
1 hertz or Hz
1 cycle per second
1 MHz
1 million cycles per second or 1000 Hz
1 GHz
1 billion cycles per second or 1000 MHz